Methods for preparing substituted sorbitylureas are discussed in U.S. Pat. No. 2,891,944, issued to F. Boettner. The invention is directed to the reaction between the cyclic urethane of N-methyl-N-sorbitylcarbamic acid and a compound having the formula RNH.sub.2, wherein R may represent a hydrogen atom or a hydrocarbon group. The cyclic urethane of N-methyl-N-sorbitylcarbamic acid is prepared by reacting N-methylglucamine and urea. It is said that the reaction may y be carried out with or without a solvent.
In "New Surfactant Polymers Based on Carbohydrates", J. Klein, Makromol. Chem. 191, 517-528 (1990), amphiphilic poly(vinylsaccharide)s are disclosed. Various alkyl-amino substituted mono- and disaccharides were obtained by reductive amination of reducing mono- and disaccharides with C.sub.4 -C.sub.10 alkyl amines. The linkage of a hydrophobic part with the mono- or disaccharide is said to have succeeded in a one-step reductive amination, wherein the mono- or disaccharide is reacted with a C.sub.4 -C.sub.10 alkyl amine in the presence of hydrogen and a Raney nickel catalyst to form the alkyl-amino substituted mono- or disaccharide. The reaction was carried out in water or water/methanol solution. Subsequent coupling of the alkylamino substituted mono- or disaccharides with a vinyl substituted isocyanate was carried out at low temperature in aqueous systems or in organic solvents.
PCT/US91/06978, Scheibel et al., discloses processes for preparing N-alkyl polyhydroxy amines and fatty acid amides therefrom in hydroxy solvents. Amines such as methyl amines are reacted with materials such as reducing sugars in hydroxy solvents such as methanol to prepare N-alkyl polyhydroxy amines. An adduct of a reducing sugar and an amine is formed in an organic hydroxy solvent. The adduct is reacted with hydrogen in the presence of a Raney nickel catalyst to form the N-alkyl polyhydroxy amine. The catalyst and substantially all water are removed from the reaction mixture. The substantially anhydrous polyhydroxy amine product is then reacted with a fatty acid ester in an organic hydroxy solvent in the presence of a base catalyst to form the polyhydroxy fatty acid amide. The N-alkyl polyhydroxy amides thus formed are said to be useful as detersire surfactants.
PCT/US91/06979 discloses processes for preparing N-alkyl polyhydroxy amines in amine and amine/water solvents and fatty acid amides therefrom. A glucose/methyl amine adduct is prepared using excess methyl amine as the solvent. Optionally, the amine solvent may be replaced with an alcohol, such as methanol. The adduct is reacted with hydrogen in the presence of a Raney nickel catalyst to form the N-alkyl polyhydroxy amine. The catalyst, substantially all of the excess amine and water are removed from the reaction mixture. The substantially anhydrous polyhydroxy amine product is then reacted with a fatty acid ester in an organic hydroxy solvent in the presence of a base catalyst to form the polyhydroxy fatty acid amide. The N-alkyl polyhydroxy amides thus formed are said to be useful as detersive surfactants.
U.S. Pat. No. 5,194,639, issued to Connor et al., discloses methods of preparing polyhydroxy fatty acid amides which comprise reacting a fatty acid ester and an N-alkyl polyhydroxy amine in one or more hydroxy solvents in the presence of a base catalyst. Preferred hydroxy solvents are said to be C.sub.1 -C.sub.4 alcohols, especially methanol. The N-alkyl polyhydroxy amides thus formed are said to be useful as detersive surfactants.
European patent application 0 220 676 A, in the name of Kunz, M., discloses surface-active agents comprising fatty acid amides of aminopolyols. The monoamides are prepared by reductive amination of mono- and oligosaccharides, followed by amidation of the aminopolyols so produced. The amidation process involves the use of solvents such as absolute methanol, butyl alcohol, ethyl acetate, chloroform or toluene.
Liquid detergent compositions, particularly concentrated liquid detergent compositions for laundry use, must be formulated for shelf-stability during manufacturing, distribution and consumption by the ultimate consumer.
Liquid detergent compositions are formulated with detersive surfactants and other cleaning aids and detergency builders (typically comprising dissolved electrolyte) and, optionally, solid particles, which are dispersed in a continuous aqueous phase. The detersive surfactant used in the liquid detergent compositions may exist in the form of lamellar droplets contained in a lamellar dispersion having a desirable turbid appearance and a sufficiently low viscosity to flow when poured by a consumer. Appropriate lamellar dispersions are described in U.S. Pat. No. 5, 147,576, Montague et al., issued Sep. 15, 1992, which is hereby incorporated by reference, and in PCT application number PCT/EP90/01962, Hales et al.
The addition of materials such as the traditional polyacrylates or acrylate/maleate copolymers as builders or co-builders has been observed to disturb the desirable rheology of the lamellar dispersion required in liquid detergent compositions. The incompatibility of traditional polyacrylates and acrylate/maleate copolymers in liquid detergent formulations has been a particular problem in concentrated liquid detergent formulations. "Concentrated liquid detergent" formulations contain a higher percent detersive surfactant than traditional liquid detergent compositions, i.e., at least about 25% detersive surfactant.
U.S. Pat. No. 5, 147,576, discloses a deflocculating polymer consisting of a hydrophilic backbone with hydrophobic side chains, which deflocculating polymer permits the formulation of concentrated liquid detergent compositions in the form of stable lamellar dispersions in a continuous aqueous phase. The deflocculating polymer permits incorporation of greater amounts of electrolytes than would otherwise be compatible with a liquid detergent composition having shelf-stability and the relatively low viscosity required by consumers. The deflocculating polymer provides stability in these liquid detergent compositions, whereas polymers traditionally used as stabilizers for emulsions do not perform as required in liquid detergent compositions.
PCT/EP90/01962 discloses liquid detergent compositions, in particular liquid detergent compositions which comprise a dispersion of lamellar droplets in an aqueous phase. One class of deflocculating polymers disclosed therein are biodegradable, hydrophobically-modified polysaccharides. Especially preferred are hydrophobically modified dextrans, more preferably dextrans having a molecular weight of 2,000 to 20,000. The hydrophobic groups may be connected to the hydrophilic backbone directly or via relatively hydrophilic linkages, for example a poly ethoxy linkage. In the polymers produced therein, the hydrophobic group may pend from other than a terminal position on the hydrophilic backbone. Additionally, in the polymers prepared therein, each chain may contain one hydrophobic group, more than one hydrophobic groups, or no hydrophobic group.
European patent application 623 670 A2 discloses the use of a biodegradable stabilizer comprising a hydrophilic polymeric chain of more than four hydrophilic monomer groups and/or having a mass greater than 300 amu. linked at one end to a hydrocarbon-soluble group to reduce or prevent the flocculation of systems comprising a flocculable suffactant and a liquid medium which is capable of flocculating said surfactant and in which said stabilizer is capable of existing as a micellar solution at a concentration of at least 1% by weight. One class of stabilizers disclosed therein are alkyl polyglycosides which are the products obtained by alkylating reducing sugars such as fructose or, preferably, glucose. The degree of polymerization of the alkyl polyglycosides is preferred to be greater than about 1.2, preferably from 2 to 20.
Neither EP 623 670 A2 nor PCT/EP90/01962 discuss economically viable processes for preparing the alkyl polyglycoside stabilizers or the hydrophobically-modified polysaccharide deflocculating polymers, respectively. It would be desirable, then, to develop processes for preparing biodegradable deflocculating polymers which are both efficient and economically viable.
It has now be found that liquid detergent compositions may be provided in a stable form comprising a lamellar dispersion of the detersive surfactant in a continuous aqueous phase by the addition of a biodegradable polymer having a hydrophilic polysaccharide backbone and a hydrophobic terminal group. It has also been discovered that the deflocculating polymers may be prepared efficiently utilizing economically viable processes. Thus, these polymers and the methods of making the polymers provide a simple, economically viable route to achieving stable detergent compositions, particularly highly concentrated compositions.